Surface albedo derived from clear-sky and partly cloudy observations from CERES

Description

One of working groups of the Clouds and the Earth’s Radiant Energy System (CERES) project, the Surface and Atmosphere Radiation Budget (SARB) working group, computes surface and atmospheric irradiances to understand surface and atmospheric radiation budget and interaction of clouds and aerosols with radiation. The CERES team is preparing for the next major algorithm revision, Edition 4. As a part of the effort, we revised the algorithm to derive clear-sky surface albedo from clear-sky CERES observations. The CERES instrument footprint size is approximately 20 km. When the entire CERES footprint is clear, based on MODIS radiances, we use a radiative transfer model to derive broadband surface albedo using top-of-atmosphere (TOA) broadband irradiance derived from CERES observations as an input. This algorithm requires the size of clear-sky scene to be larger than 20 km. To improve the sampling for the Edition 4 process, we use partly cloudy scenes in addition to the clear-sky scene. Using MODIS narrowband radiances observed over the clear-sky area of partly cloudy CERES footprint, we estimate broadband clear-sky radiance and apply CERES angular distribution model (ADM) to compute TOA irradiance. We then derive the broadband surface albedo using radiation transfer model, similar to the process used for CERES clear-sky footprints.

In this presentation, we will present surface albedo map derived from the Edition 4 process. The surface albedo derived around the ARM Climate Research Facility North Slope of Alaska (NSA) and Southern Great Plains (SGP) sites will be used in an ASR-funded projects, “Moving ASR cloud microphysical retrieval beyond the vertical column” (principal investigator Professor Eugene Clothiaux) in modeling 3D radiative transfer.